Chromosome-scale genome of the human blood fluke Schistosoma mekongi and its implications for public health

Background Schistosoma mekongi is a human blood fluke causing schistosomiasis that threatens approximately 1.5 million humans in the world. Nonetheless, the limited availableS. mekongi genomic resources have hindered understanding of its biology and parasite-host interactions for disease management and pathogen control. The aim of our study was to integrate multiple technologies to construct a high-quality chromosome-level assembly of theS. mekongi genome.Methods The reference genome forS. mekongi was generated through integrating Illumina, PacBio sequencing, 10 × Genomics linked-read sequencing, and high-throughput chromosome conformation capture (Hi-C) methods. In this study, we conducted de novo assembly, alignment, and gene prediction to assemble and annotate the genome. Comparative genomics allowed us to compare genomes across different species, shedding light on conserved regions and evolutionary relationships. Additionally, our transcriptomic analysis focused on genes associated with parasite-snail interactions inS. mekongi infection. We employed gene ontology (GO) enrichment analysis for functional annotation of these genes.Results In the present study, theS. mekongi genome was both assembled into 8 pseudochromosomes with a length of 404 Mb, with contig N50 and scaffold N50 lengths of 1168 kb and 46,759 kb, respectively. We detected that 43% of the genome consists of repeat sequences and predicted 9103 protein-coding genes. We also focused on proteases, particularly leishmanolysin-like metalloproteases (M8), which are crucial in the invasion of hosts by 12 flatworm species. Through phylogenetic analysis, it was discovered that the M8 gene exhibits lineage-specific amplification among the genusSchistosoma. Lineage-specific expansion of M8 was observed in blood flukes. Additionally, the results of the RNA-seq revealed that a mass of genes related to metabolic and biosynthetic processes were upregulated, which might be beneficial for cercaria production.Conclusions This study delivers a high-quality, chromosome-scale reference genome ofS. mekongi, enhancing our understanding of the divergence and evolution ofSchistosoma. The molecular research conducted here also plays a pivotal role in drug discovery and vaccine development. Furthermore, our work greatly advances the understanding of host-parasite interactions, providing crucial insights for schistosomiasis intervention strategies.

Comparison of novel and standard diagnostic tools for the detection of Schistosoma mekongi infection in Lao People’s Democratic Republic and Cambodia

Background:Given the restricted distribution of Schistosoma mekongi in one province in Lao People’s Democratic Republic(Lao PDR)and two provinces in Cambodia,together with progress of the national control programmes aimed at reducing morbidity and infection prevalence,the elimination of schistosomiasis mekongi seems feasible.However,sensitive diagnostic tools will be required to determine whether elimination has been achieved.We compared several standard and novel diagnostic tools in S.mekongi-endemic areas.Methods:The prevalence and infection intensity of S.mekongi were evaluated in 377 study participants from four villages in the endemic areas in Lao PDR and Cambodia using Kato-Katz stool examination,antibody detection based on an enzyme-linked immunosorbent assay(ELISA)and schistosome circulating antigen detection by lateral-flow tests.Two highly sensitive test systems for the detection of cathodic and anodic circulating antigens(CCA,CAA)in urine and serum were utilized.Results:Stool microscopy revealed an overall prevalence of S.mekongi of 6.4%(one case in Cambodia and 23 cases in Lao PDR),while that of Opisthorchis viverrini,hookworm,Trichuris trichiura,Ascaris lumbricoides and Taenia spp.were 50.4%,28.1%,3.5%,0.3%and 1.9%,respectively.In the urine samples,the tests for CCA and CAA detected S.mekongi infections in 21.0%and 38.7%of the study participants,respectively.In the serum samples,the CAA assay revealed a prevalence of 32.4%,while a combination of the CAA assay in serum and in urine revealed a prevalence of 43.2%.There was a difference between the two study locations with a higher prevalence reached in the samples from Lao PDR.Conclusions:The CCA,CAA and ELISA results showed substantially higher prevalence estimates for S.mekongi compared to Kato-Katz thick smears.Active schistosomiasis mekongi in Lao PDR and Cambodia might thus have been considerably underestimated previously.Hence,sustained control efforts are still needed to break transmission of S.mekongi.The pivotal role of highly sensitive diagnostic assays in areas targeting elimination cannot be overemphasised.

Transmission of Opisthorchis viverrini,Schistosoma mekongi and soil-transmitted helminthes on the Mekong Islands,Southern Lao PDR

Background:Prevalence of Opisthorchis viverrini,Schistosoma mekongi and soil-transmitted helminths(STH)remains high in Lao People’s Democratic Republic(Lao PDR),despite control efforts including mass-drug administration,education and communication campaigns.New approaches are required to advance helminth control.Methods:An ecohealth study was conducted on two Mekong islands in Southern Laos.Demographic and behavioural data were collected by questionnaire.Human and animal reservoir stools were examined.Bithynia spp.and Neotricula aperta snails were examined using shedding.Fresh water fish were examined using digestion technique.Multivariate random-effects analysis was used to find risk factors associated with helminth infections.Results:Human infection rates with O.viverrini,hookworm,S.mekongi,Trichuris trichiura,Ascaris lumbricoides and Taenia spp.were 60.7%,44.1%,22.2%,4.1%,0.6%and 0.1%,respectively.Heavy intensity infections were 4.2%,3.6%and 1.8%for O.viverrini,S.mekongi and hookworm,respectively.O.viverrini and S.mekongi infection rates among dogs and cats were 25.0%and 14.7%,respectively.Of the cats tested,53.1%were infected with O.viverrini.Prevalence of O.viverrini and S.mekongi in snails was 0.3%and 0.01%,respectively.Overall prevalence of O.viverrini infection in fresh water fish was 26.9%,with the highest infection rates occurring in Hampala dispa(87.1%),Cyclocheilichthys apogon(85.7%)and Puntius brevis(40.0%).Illiteracy and lower socioeconomic status increased the risk of O.viverrini infection,while those aged 10-16 years and possessing latrines at home were less likely to be infected.Household dogs and cats that consumed raw fish were significantly and positively associated with O.viverrini infection of the household members.For S.mekongi,children under 9 years old were exposed significantly to this infection,compared to older age groups.Conclusions:There is a pressing need to design and implement an integrated helminth control intervention on the Mekong Islands in southern Lao PDR.Given the highly dynamic transmission of O.viverrini,S.mekongi,STH and extended multiparasitism,annual mass-drug administration is warranted along with environmental modifications,health education and improved access to clean water and adequate sanitation to consolidate morbidity control and move towards elimination.Trail registration number:Our findings presented here are from a cross-sectional study,therefore,it has not been registered.

Cross-reaction of POC-CCA urine test for detection of Schistosoma mekongi in Lao PDR: a cross-sectional study

Background:The point-of-care circulating cathodic antigen(POC-CCA)test is increasingly used as a rapid diagnostic method for Schistosoma mansoni infection.The test has good sensitivity,although false positive results have been reported among pregnant women and patients with urine infections and hematuria.We validated the POC-CCA test's ability to diagnose Schistosoma mekongi infection in Lao People's Democratic Republic(Lao PDR),where S.mekongi is endemic.Of particular interest was the test's specificity and possible cross-reactivity with other helminth infections.Methods:We conducted a cross-sectional study of children and adults in the provinces of Champasack(Schistosoma mekongi and Opisthorchis viverrini endemic),Savannakhet(O.viverrini endemic)and Luang Prabang(soil-transmitted helminths endemic)between October 2018 and April 2019.POC-CCA and urine dipstick tests were administered to all study participants,while an additional pregnancy test was offered to women.Two stool samples were collected from participants and examined with a Kato-Katz test(two smears per stool).Logistic regression was used to associate potential confounding factors(predictors)with POC-CCA test results(outcome).Results:In S.mekongi-endemic Champasack,11.5%(n=366)and 0.5%(n=2)of study participants had positive POC-CCA and Kato-Katz test results,respectively.Only one of the two Kato-Katz positive patients was also POC-CCA positive.In Champasack and Luang Prabang,where S.rnekongi is not endemic,the POC-CCA test yielded(presumably)false positive results for 6.0%(n=22)and 2.5%(n=9)of study participants,respectively,while all of the Kato-Katz tests were negative.POC-CCA positive test results were significantly associated with O.viverrini infection(1.69,95%confidence interval(CI):1.02-2.77,P=0.042),increased leukocytes(adjusted Odds Ratio(aOR)=1.58,95%CI:1.15-2.17,P=0.005)and hematuria(aOR=1.50,95%CI:1.07-2.10,P=0.019)if the observed trace was counted as a positive test result.Two pregnant women from Champasack province had POC-CCA positive tests.Conclusions:We observed a cross-reaction between the POC-CCA test and O.viverrini infection.To some extent,we can confirm previous observations asserting that POC-CCA provides false positive results among patients with urinary tract infections and hematuria.In S.mekongi-endemic areas,POC-CCA can be applied cautiously for surveillance purposes,keeping in mind the considerable risk of false positive results and its unknown sensitivity.

胶体染料试纸条法(DDIA)诊断湄公血吸虫病的研究

目的 评价胶体染料试纸条法诊断湄公血吸虫病的应用价值。方法 制备以日本血吸虫虫卵可溶性抗原为抗原的胶体染料试纸条试剂盒 (DDIA kit)。采用该试剂盒检测来自柬埔寨湄公血吸虫病流行区的 34例粪检阳性者和 170例粪检阴性者 ,近年来经吡喹酮治疗后不同年份的人群12 2例 ,以及 114例来自非血吸虫病流行区的健康人 ;同时对来自老挝湄公血吸虫病流行区的 70例粪检阳性者和 6 0例猫后睾吸虫感染者进行检测。对其中部分样本还采用日本血吸虫 SEA- EL ISA进行对照检测。结果 DDIA试剂盒检测湄公血吸虫病的敏感性为 97.1% (33/ 34,柬埔寨 )和98.6 % (6 9/ 70 ,老挝 ) ,与 EL ISA的检测结果相一致。对非流行区健康人的特异性为 10 0 .0 %。结论 日本血吸虫 DDIA试剂盒具有快速、简便、不需任何仪器设备等优点 。

云南省拟钉螺作为狸殖吸虫与血吸虫中间宿主的研究

自1981年开始,我们与美国费城自然科学院、云南省卫生防疫站以及大理州血吸虫病防治所等单位协作,先后对云南省南部西双版纳州、西北部大理州以及中部的昆明市周围有代表性的地区进行拟钉螺的调查。已发现6个新种,其中一种景洪拟钉螺(Tricula jinghongensis Guo and Gu,1985),是斯氏狸殖吸虫(Pagumogonimus skrjabini)和类中华血吸虫(Schistosoma sinensium-like blood fluke)的中间宿主。另一种博氏拟钉螺(T.bollingi),是我国新纪录,其始发现于泰国。感受性试验表明,其可感染中华血吸虫和湄公血吸虫(Schistosoma mekongi),因此在血吸虫病流行病学上应予以重视。

考虑不同年龄段的老挝湄公血吸虫病模型研究

基于实际数据中不同年龄段病人的比例不一样这一现象,建立一个老挝湄公血吸虫病数学模型,模型中考虑人宿主和钉螺宿主的感染比例,并将人宿主分为不同的8个年龄段,得出了平衡点的存在性,求出基本再生数,对模型的平衡点的稳定性进行了讨论和数值模拟,最后给出最佳控制策略.

老挝消除血吸虫病策略的STEEPLE分析

目的分析老挝消除血吸虫病面临的宏观环境,为促进中老消除血吸虫病合作提供依据。方法采用STEEPLE分析模型分析老挝宏观环境对落实消除血吸虫病策略的影响。结果不利因素:(1)老挝多民族间文化和语言的差异、偏远农村地区经济发展落后状态影响卫生保健措施的落实;(2)当前可投入的人力和物质资源不能满足社会对卫生事业的需求;(3)血吸虫病防治专项经费短缺等。有利因素:(1)政府对卫生系统改革和消除血吸虫病有坚定的政治承诺;(2)建立了消除血吸虫病的多部门技术工作小组;(3)与中国建立了良好的合作关系。结论老挝需要优化政府战略和政策的执行环境;完善卫生筹资体系,加大政府投资力度;保障相应的人力和物质资源投入;在政府与国际合作的支持下可望实现消除血吸虫病的目标。

湄公血吸虫病流行概况及消除面临的挑战

湄公血吸虫病自发现以来就成为东南亚的重大公共卫生问题,老挝和柬埔寨两国经过多年防控使其得到了稳步控制,但距离消除血吸虫病的目标还有众多挑战和困难。随着我国“一带一路”倡议的稳步推进,增加和扩大了我国湄公血吸虫病境外输入和境外感染的风险。本文对湄公血吸虫病的防控措施、目前面临的问题等进行综述,分析该病是否对我国和“一带一路”的推进存在危害,为今后的南南合作和血吸虫病消除提供参考。